Population Health Metrics is an open-access online electronic journal published by BioMed Central – it is universally and freely available online to everyone, its authors retain copyright, and it is archived in at least one internationally recognised free repository. To fund this, from November 1 2003, authors of articles accepted for publication will be asked to pay an article-processing charge of US$500. This editorial outlines the reasons for the introduction of article-processing charges and the way in which this policy will work.

Waiver requests will be considered on a case-by-case basis, by the Editor-in-Chief. Article-processing charges will not apply to authors whose institutions are 'members' of BioMed Central. Current members include NHS England, the World Health Organization, the US National Institutes of Health, Harvard, Princeton and Yale universities, and all UK universities. No charge is made for articles that are rejected after peer review. Many funding agencies have also realized the importance of open access publishing and have specified that their grants may be used directly to pay APCs.

Population Health Metrics is published by BioMed Central, an independent publisher committed to ensuring peer-reviewed biomedical research is open access – it is universally and freely available online to everyone, its authors retain copyright, and it is archived in at least one internationally recognised free repository [1]. Population Health Metrics however, has taken this further, by making all content open access. To fund this, from November 1 2003, authors of articles accepted for publication will be asked to pay an article-processing charge (APC) of US$500. This will apply only to articles submitted from November 1 2003, not to those submitted before that date.

Traditionally, readers pay to access articles, either through subscriptions or by paying a fee each time they download an article. Escalating journal subscriptions have resulted in libraries subscribing to fewer journals [2], and the range of articles available to readers is therefore limited. Although traditional journals publish authors' work for free (unless there are page or colour charges), having to pay to access articles limits how many can read, use and cite them.

Population Health Metrics' open access policy changes the way in which articles are published. First, all articles become freely and universally accessible online, and so an author's work can be read by anyone at no cost. Second, the authors hold copyright for their work and grant anyone the right to reproduce and disseminate the article, provided that it is correctly cited and no errors are introduced [1]. Third, a copy of the full text of each open access article is archived in an online repository separate from the journal. Population Health Metrics' articles are archived in PubMed Central [3], the US National Library of Medicine's full-text repository of life science literature; e-Depot [4], the National Library of the Netherlands' digital archive of all electronic publications; and Potsdam [5] and INIST [6], sites archiving the research articles published by BioMed Central in Germany and France, respectively.

Open access has four broad benefits for science and the general public. First, authors are assured that their work is disseminated to the widest possible audience, given that there are no barriers to access their work. This is accentuated by the authors being free to reproduce and distribute their work, for example by placing it on their institution's website. It has been suggested that free online articles are more highly cited because of their easier availability [7]. Second, the information available to researchers will not be limited by their library's budget, and the widespread availability of articles will enhance literature searching and facilitate meta-analyses [8]. Third, the results of publicly funded research will be accessible to all taxpayers and not just those with access to a library with a subscription. As such, open access could help to increase public interest in, and support of, research. Note that this public accessibility may become a legal requirement in the USA if the proposed Public Access to Science Act is made law [9]. Fourth, a country's economy will not influence its scientists' ability to access articles because resource-poor countries (and institutions) will be able to read the same material as wealthier ones (although creating access to the internet is another matter [10]).

APCs will allow continued open access to all of Population Health Metrics's articles. Authors are asked to pay US$500 if their article is accepted for publication. Waiver requests will be considered on a case-by-case basis, by the Editor-in-Chief. Authors can circumvent the charge by getting their institution to become a 'member' of BioMed Central, whereby the annual membership fee covers the APCs for all authors at that institution for that year. Current members include NHS England, the World Health Organization, the US National Institutes of Health, Harvard, Princeton and Yale universities, and all UK universities [11]. No charge is made for articles that are rejected after peer review. Many funding agencies have also realized the importance of open access publishing and have specified that their grants may be used directly to pay APCs [12].

The APC pays for efficient and thorough peer review, for the article to be freely and universally accessible in various formats online, and for the processes required for inclusion in PubMed and archiving in PubMed Central, e-Depot, Potsdam and INIST. Although some authors may consider US$500 expensive, it must be remembered that Population Health Metrics does not levy additional page or colour charges on top of this fee, which can easily exceed US$500. With the article being online only, any number of colour figures and photographs can be included, at no extra cost.

Although several journals now offer free access to their articles online, this is different from open access (as defined by the Bethesda Statement [13]). Journals often delay free access for 6–12 months, and even when the full text is available, readers are not allowed to reproduce and/or disseminate the work because of restrictions imposed by the copyright policy. That said, Population Health Metrics is not alone in the move to open access funded by APCs. The British Medical Journal has recently announced that it cannot continue to provide free access to its website [14] and is considering various sources of revenue, including APCs [15]. Also, the Public Library of Science has set up two new open access journals, and have elected to set APCs of US$1500 for each accepted article [16]. Given that the Public Library of Science has used television advertising to promote journals [9], the high profile of these journals will raise awareness of open access and encourage researchers in all disciplines to understand and accept open access, with APCs as an acceptable method to fund it. By providing a forum for open access, APCs will enable Population Health Metrics to serve the public health community. We believe this change will benefit those interested in the measurement of population health and its determinants and aid scientific research in this area, and we hope you will support this progress by submitting your next article to an open access journal.

This article is published under license to BioMed Central Ltd. This is an Open Access article: verbatim copying and redistribution of this article are permitted in all media for any purpose, provided this notice is preserved along with the article's original URL.